Engineering and Technical Services for Joint Group on Acquisition Pollution Prevention (JG-APP) Joint Test Protocol CC-P-1-1 for Validation of Alternatives to Lead-Containing Surface Finishes, for Development of Guidelines for Conformal Coating Usage, and for Qualification of Low-VOC Conformal Coatings
Abstract
Surface finishes containing tin and lead are applied to circuit cards to prevent oxidation of exposed copper. This application ensures a solderable surface when components are added during later stages of processing. The most widely used processes for applying surface finishes are hot-air solder leveling (HASL) with solder mask, and reflowed tin-lead. Both processes generate lead emissions and waste. Lead is a toxic substance that is heavily regulated by various federal, state, and local environmental agencies. A related concern for fused tin-lead surface finishes is their inability to provide a level soldering surface. Planarity is extremely important in the reliable placement and soldering of fine pitch components. Tin-lead surface finishing is seen as a limiting technology in this respect. The CCAMTF believes that lead-free alternative surface finishes would provide increased planarity. Conformal coatings are thin layers of synthetic resins or polymers applied to circuit cards for protection against a variety of environmental, mechanical, electrical, and chemical conditions; these conditions include humidity, moisture, contamination, stress, mechanical shock, vibration, thermal cycling, and corrosion. The application process is expensive, and time consuming, and accounts for up to 40% of the VOC emissions generated from high-volume circuit card manufacturing. (The remaining 60% of VOC emissions is generated by soldering fluxes, primers, and cleaning agents.) VOC emissions are heavily regulated by various federal, state, and local environmental agencies. The CCAMTF believes that intelligent use of conformal coatings would decrease manufacturing costs, simplify rework, and reduce pollution at the source without degrading circuit card quality or performance. Guidelines for intelligent use of conformal coatings would describe suitable applications that reduce the use of conformal coatings, use low-VOC conformal coatings, or use conformal coatings without primers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 23, 1999
- Accession Number
- ADA601885